Date of Graduation


Document Type


Degree Name

Master of Science in Poultry Science (MS)

Degree Level



Poultry Science


Samuel J. Rochell

Committee Member

Michael T. Kidd

Second Committee Member

Amanda J. Ashworth


biomass, broiler, isoleucine, reduced crude protein, threonine, valine


Poultry nutritionists continue to identify methods to lower feed price without compromising broiler growth performance, processing yields, or animal well-being. A common approach is to reduce dietary crude protein (CP), the second most expensive component in a broiler diet. Subsequently, reducing CP will reduce the inclusion levels of intact protein sources (e.g., soybean meal [SBM]), which can be accomplished by supplementing individual amino acids (AA). This methodology not only reduces diet cost, pending if feed-grade AA are more economical, but can contribute to improving broiler health and environmental sustainability. Therefore, two experiments were conducted to evaluate individual feed-grade AA in commercial reduced CP diets fed to broilers from 0 to 48 d. In experiment 1, L-Val and L-Ile were supplemented in addition to L-Met, L-Lys, and L-Thr to further reduce dietary CP in corn and SBM-based diets. Peanut meal or animal protein blend was used to replace partial amounts of SBM. Results confirmed that broilers maintained performance when fed reduced CP diets, independent of diet composition. Furthermore, broilers fed L-Val and L-Ile had increased breast meat yield and lower nitrogen excretion. The partial replacement of SBM with animal protein blend alleviated footpad dermatitis, whereas feed-grade L-Val and L-Ile did not. In experiment 2, L-Val, L-Ile, and L-Arg were supplemented after the additions of L-Met, L-Lys, and L-Thr to further reduce dietary CP. One experimental diet was devoid of supplemental Thr to demonstrate the necessity of maintaining digestible Thr levels. For two experimental diets, a novel, alternative Thr biomass was used in place of a traditional crystalline L-Thr as a Thr source in reduced CP diets. The Thr biomass not only supplied Thr but energy and other nutrients such as essential and nonessential AA. The Thr biomass was fed in two dietary treatments but formulated differently: in one diet, the biomass was formulated only on the Thr and energy contributions while the other diet considered the full nutrient matrix. Results confirmed that broilers maintained performance when fed reduced CP diets and that broilers need a minimum dietary Thr. The Thr biomass was efficacious in replacing crystalline L-Thr.